Apex domains cannot have CNAME records.
Question and response
Question
dig OCS.RU. NS
Answer
OCS.RU. 5 NS cetus.OCS.RU.
OCS.RU. 5 NS ns.OCS.RU.
Authority
The response has no authority records.
Additional
ns.OCS.ru. 5 A 91.220.11.25
cetus.ocs.ru. 5 A 185.171.101.179
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0